1. Field of the Invention
The present invention relates generally to a flying magnetic head slider used in a magnetic disk drive, and more particularly to a negative-pressure slider intended for a small flying height.
2. Description of the Related Art
In recent years, a magnetic disk drive has increasingly been reduced in size and enlarged in capacity, requiring that the spacing between an electromagnetic transducer formed on a head slider and a recording layer of a magnetic disk is as small as possible, so that it is essential to smooth out a disk surface and to reduce a slider flying height. To maintain the durability of the disk drive and satisfy its recording and reproducing characteristics, it is preferable to minimize the slider flying height so that the contact between the slider and the disk surface is avoided. Further, a slider having excellent flying stability is desired because a large acceleration is applied in an accessing direction to obtain a high access speed.
In an existing magnetic disk drive, the roughness of the disk surface is substantially constant irrespective of radial positions on the disk, so that it is necessary to maintain the slider flying height at a substantially constant low level irrespective of radial positions on the disk. Further, in a recent magnetic disk drive, a rotary positioner is widely used for the purposes of size reduction of the magnetic disk drive and simplification of a mechanism, and a negative-pressure slider with less variations in flying height due to changes in yaw angle is desired.
As a negative-pressure magnetic head slider having excellent flying stability, there has been proposed a slider having a pair of rails decreased in rail width from an air inlet end toward an air outlet end and defining a groove between the pair of rails to generate a negative pressure in the groove (Japanese Patent Laid-open No. 4-228157). FIG. 1A is a plan view of a conventional negative-pressure magnetic head slider disclosed in the above publication, and FIG. 1B is a perspective view of the slider shown in FIG. 1A. The slider denoted by reference numeral 2 has a rectangular shape as viewed in plan, and it has an air inlet end 2a and an air outlet end 2b.
A pair of rails 4 and 6 for generating a positive pressure are formed on a disk opposing surface of the slider 2. The rails 4 and 6 have flat air bearing surfaces (rails surfaces) 4a and 6a for generating a flying force during rotation of a disk, respectively. Tapering surfaces 4b and 6b are formed at the air inlet end portions of the rails 4 and 6, respectively. A groove 8 for expanding the air once compressed to generate a negative pressure is defined between the rails 4 and 6.
An electromagnetic transducer 10 is formed on the air outlet end 2b of the slider 2 at a position where the rail 4 is located. A center rail 11 is formed between the rails 4 and 6 on the air inlet end 2a side. Each of the rails 4 and 6 has a width larger at the air inlet end portion and the air outlet end portion and smaller at the intermediate portion, thereby suppressing variations in flying height due to changes in yaw angle. Further, by forming the tapering surfaces 4b and 6b at the air inlet end portions of the rails 4 and 6, variations in flying height due to deposition of dust can be suppressed. FIG. 1B is a perspective view of the slider 2 as viewed from the side of the rail surfaces, in which the broken arrows show a positive pressure acting on the slider 2, and the solid arrows show a negative pressure acting on the slider 2. The positive pressure is generated at the rail surfaces 4a and 6a, and the negative pressure is generated at the groove 8.
Longitudinal center lines of the rails 4 and 6 are substantially parallel to a longitudinal center line of the slider 2. In a magnetic disk drive, the magnetic head slider is mounted on a rotary arm for positioning the slider in the radial direction of a magnetic disk, and the yaw angle of the slider (the angle between a rotational direction of the disk and a longitudinal center line of the slider) continuously changes from the inner side to the outer side of the magnetic disk. When the yaw angle becomes large, the track width of the magnetic disk is decreased to cause a reduction in output. To prevent such an output reduction, the conventional slider is mounted on the rotary arm so that the yaw angle of the slider becomes 0 degree between an innermost track and an outermost track of the magnetic disk.
FIG. 2 shows flying characteristics of the conventional slider shown in FIGS. 1A and 1B. In FIG. 2, the horizontal axis represents radial distance from the center of the magnetic disk, and the vertical axis represents flying height of the slider. As apparent from FIG. 2, the flying height of the slider increases near a radially central position on the magnetic disk. This is due to the following facts. As shown in FIG. 3A, the flying height of the slider increases with an increase in radial distance in the case that the yaw angle of the slider is assumed to be constant irrespective of radial positions on the magnetic disk. That is, since the peripheral speed of the magnetic disk increases with an increase in radial distance, the flying height of the slider increases with an increase in peripheral speed in the case that the yaw angle is constant.
In contrast, as shown in FIG. 3B, the flying height of the slider is maximum at or near a slider yaw angle of o degree in the case that the peripheral speed of the magnetic disk is assumed to be constant over the entire radial range from the innermost track to the outermost track of the disk. The above fact that the flying height of the slider is maximum at or near a slider yaw angle of 0 degree as shown in FIG. 3B is considered to be caused by the following. That is, in the case that air is introduced into the space between the disk surface and the slider in the same direction as the longitudinal center lines of the rails 4 and 6 (the yaw angle is 0 degree, the positive pressure generated on the slider becomes maximum, resulting in a maximum flying height of the slider.
In contrast, when the angle between the air introducing direction and the longitudinal center line of each rail is increased, the positive pressure is decreased to result in a decrease in flying height. Accordingly, the combination of the flying characteristics shown in FIG. 3A and the flying characteristics shown in FIG. 3B provides the flying characteristics shown in FIG. 2 such that the flying height of the conventional slider increases near a radially central position on the magnetic disk. In a conventional general magnetic disk drive with a relatively large flying height, the increase in flying height near a radially central position on the magnetic disk is negligibly small. However, in the case of adopting a negative-pressure slider in response to an increase in density of a recent magnetic disk drive, the slider flying height is small, causing a deterioration in receiving and reproducing characteristics near a radially central position on the magnetic disk.